The invention concerns a shifting device of a transmission.
Shiftings of a transmission to change the ratio thereof are carried out in practice in order to convert the engine rotational speed or the engine torque abutting on the transmission input into rotational speed or torque on output wheels of a vehicle which correspond to a desired speed of the vehicle under sufficient input torques or tractional forces.
For a change of ratio, for example, a shifting device is provided in the practice which has a shifting element rotatably guided upon a component part and known also by the designation of drum selector gear. The drum selector gear, known per se, is usually provided with at least one grooved path in which at least one shift fork engages. Upon rotation of the shifting element, the shift fork is moved axially along a shift fork guide by a defined shape of the grooved path. To carry out a gear shift, the drum selector gear is turned either manually by the driver, via a shift lever, or actuated by outside force via a drive mechanism.
It is known from the prior art, for example, to use an electromotor as a drive system for outside-force actuation of the drum selector gear which is situated in the transmission in the area of the drum selector gear often parallel thereto. Between the electromotor and the drum selector gear, for example, a reduction step is provided by which a rotary motion of the electromotor is transmitted to the drum selector gear for an axial adjustment of the shift fork.
The shifting devices, known from the practice, however, have the disadvantage that the use of an electromotor for actuating a drum selector gear requires a large installation space in a transmission, which stands opposed to the general requirements presently existing for assemblies of a vehicle such as a reduction in the dimensions and a reduction in weight of the component parts.
The need for a large space for the described shifting device results from the fact that a drum selector gear must have a large diameter to ensure its functionality, particularly when coupling several shift forks. The large diameter is due to the fact that for the different shift forks coupled, longer grooved paths have to be provided in order to be able to operate or actuate them all separately, the drum selector gear being allowed to perform at most one revolution. Since the electromotor is separately designed with a housing and placed in the area of the drum selector gear, added space is a need in the transmission for driving the drum selector gear which generally is not available or leads to an enlargement of the dimensions and an increase of the weight of the transmission.
Therefore, the problem on which this invention is based is to make a shifting device of a transmission available which requires only a small space in the transmission.
According to the invention this problem is solved by a shifting device of a transmission having the features of claim 1.
With the inventive shifting device of a transmission, the space requirement is considerably reduced since the stator and the rotor of the electromotor, serving as an input of the grooved shifting element, is conveniently placed at least partly between the shifting element and the component part without a housing of its own. With this configuration of the inventive shifting device in which, contrary to a conventional shifting element, the external dimensions do not have to be changed at all or only insignificantly by integration of an electrical drive of the shifting device in the area between the shifting element and the axle associated therewith, the needed space is reduced.
It is a further advantage that the stator-rotor unit of the electrical drive of the shifting device, situated in the transmission without a housing of its own, makes it possible to spare component parts which results in a reduction in weight of the transmission.
The inventive solution conveniently does not require a complete new construction of the driving aggregate or of the transmission since the electric machine can also be integrated without problem, e.g. in a sealed, oil-containing area of currently available types of transmission.